Chronic lateral ankle instability is most often due to old tears of the lateral ligaments, but can also be caused by dislocation, subluxation or tear of the peroneal tendon and disturbance of the sensory proprioceptive reflexes due to injury of the superficial peroneal nerve, or, in rare cases, neuromotor dysfunction due to neurogenic disease or poliomyelitis. The chronic anterolateral instability of the ankle described herein refers specifically to old tears of the anterior talofibular ligament and/or the heel-fibular ligament. The lateral ankle ligament complex consists of the anterior talofibular ligament (2-2.5 mm thick), the heel-fibular ligament (3 mm thick), and the posterior talofibular ligament, while the lateral talofibular ligament (over the subtalar joint) is located between the anterior talofibular ligament and the heel-fibular ligament and is fused to both. Lateral ankle ligament tears are far more common than external ankle avulsion fractures, and because the posterior talofibular ligament is the strongest of the three ligaments, anterolateral instability due to anterior ligament tears of the anterior talofibular ligament and/or the heel fibular ligament along with torn posterior ligaments of the joint capsule and joint capsule laxity is most common. The classic pattern of reinjury is inversion, plantarflexion, and internal rotation in the swing phase during walking. There are three types of ankle ligament injuries based on injury pathology: type I: minor ligament injury; type II: incomplete injury of the ligament; and type III: complete rupture of the ligament. The ligament is an oligovascular organ and its blood supply mainly comes from the surrounding soft tissues rather than the bone structure, which heals itself with scar tissue and is repaired by fibrous tissue 6 weeks after injury. For minor ligament injuries, regular conservative treatment can heal the ligament spontaneously, while severe ligament tears and patients who have not been treated conservatively or have failed conservative treatment will have chronic ankle instability and require surgical intervention. The incidence of chronic instability after acute lateral ankle ligament injury is about 15%-20%, and some scholars in China have reported 10%-30%. Chronic ankle instability often leads to functional and organic damage, repeated cartilage damage and degenerative osteoarthritis and chronic synovitis causing joint pain. The disease is common in young adults, and there is no significant difference in the incidence between men and women. The most common causes of injury are sports injuries that have not been treated conservatively or failed to be treated conservatively, followed by injuries caused by traffic accidents, ankle fractures combined with ligament injuries due to focus on treatment of fractures without proper treatment of ligament injuries or ligament injuries caused by the pursuit of anatomical repositioning during surgery can also lead to lateral instability. The lateral instability can also occur if the fibula is retained too short (<10%) after bone removal. The main manifestation of this disease is repeated sprains, and some patients feel stiffness in movement. Most patients come to the clinic with a re-torsion of the ankle, complaining of swelling, pain and instability. Physical examination includes localized pressure pain under the outer ankle, inversion stress test, anterior drawer test, and peroneal long and short muscles tenderness. Imaging data plain X-ray could only exclude the presence of combined fractures and intra-articular free bodies, and could not show peripheral ligamentous joint capsule injury. Arthrography and peroneal tendinography were once used to diagnose the presence or absence of joint capsule ligament rupture, but were gradually eliminated with the advent of newer techniques because of the invasive operation and complexity of the examination. Stress radiography has been accepted by most scholars as an important tool for assessing ankle laxity, especially joint instability. Takao believes that only the anterior talofibular ligament should be repaired when the talar tilt angle is less than 10°, while both ATFL and CFL should be reconstructed when the talar tilt angle is greater than 10°. 7°-15° or a difference of more than 2° from the healthy side is reported as positive in China. However, in the case of talar tilt and forward displacement of the talus; some patients with lateral radiographs may have forward dislocation of the talus; overseas literature reports that an anterior displacement of the talus (ATT) ≥ 6-10 mm and a difference with the healthy side (ΔATT) ≥ 3 mm as positive indicators. Some scholars recommend that the ATT and ΔATT should be ≥8mm and ≥2mm respectively, and believe that this standard should be smaller than that of acute injury due to adhesions and other factors. Ultrasound can diagnose the injury of ankle ligaments, and according to the degree of injury, there are three types of contusions, partial tears and complete tears, which have good correlation with the pathological diagnosis and can be examined dynamically. Ultrasound is more sensitive to the diagnosis of acute injury and can clarify the extent, type and degree of ligament injury, especially for the diagnosis of complete tears with high accuracy. However, there is a lack of quantitative indicators for the functional status of ligaments in chronic joint instability II injuries, which can be based on bilateral comparisons. This requires the examiner to have extensive experience to avoid missed or misdiagnosis. With the rapid development of MRI technology, it has played an irreplaceable role in the diagnosis of acute trauma, but lacks clinical typing and guidance on prognosis. There is no report on the diagnosis of chronic instability. Most scholars do not advocate surgical treatment in the acute phase of trauma. The most effective conservative treatment is braking the ankle in a neutral or slightly valgus position. However, some scholars advocate early functional activities including movement of the ankle and subtalar joint; isometric and isometric contractions of the foot and ankle muscles, especially the peroneal muscles, endurance training; and training of the proprioceptors, which enhance dynamic stability and are an essential part of rehabilitation. Ankle braces or elastic bandages help prevent the recurrence of ankle sprains, which are especially important in activities where this is a risk, and such patients require aggressive surgical treatment. Most athletes can heal completely with these modalities, and 80-85% of patients can regain joint stability with regular functional rehabilitation. The clearest indication for surgery remains the failure of non-operative treatment. There are many surgical procedures available for lateral ankle instability. They can be broadly divided into two categories, namely direct anatomic repair of the lateral ligament and non-anatomic repair using adjacent tendon ligament tissue to reconstruct the function of the lateral ligament. One type is anatomic repair of the lateral ligament. This approach is less invasive, has a shorter operative time, takes full advantage of the local anatomy and preserves the mobility of the talofibular and subtalar joints, and has a low incidence of postoperative complications. Brostroms was the first to report in 1966 that in 60 patients with chronic anterolateral ankle instability, the CFL was repaired in 30% of them by direct suturing of the ATFL with a shortened mid-section, with a success rate of 80%. This technique ushered in an epoch of anatomic repair, with subsequent innovations in modified procedures. These include suturing the ends of the overlapping clipped ligaments to strengthen the ligaments, or drilling the distal fibula to shorten the proximal ligament, and also incorporating a periosteal fibular cover to strengthen the anastomotic end, all with success rates ranging from 87% to 95%. Evaluation criteria include mobility, strength, return to pre-injury level of activity, need for reoperation, and complications. Gould et al. performed this modified Brostroms ligament repair in professional ballet dancers and athletes by overlapping sutures of the ATFL and CFL and then attaching the lateral portion of the flexor support band to the distal fibula and covering it with the periosteum to provide stability to the talofibular and subtalar joints. Hamilton et al. performed this modified Brostroms ligament repair on professional ballerinas and athletes with good results, and the procedure was extended to high-level athletes. Karlsson et al. used a modified Brostroms ligament repair to repair both ATFL and CFL with better results than ATFL alone, achieving an 80% improvement rate. It was noted that the unsatisfactory results were related to extensive laxity of the ligaments, the long duration of the ligaments, and previous surgery. Because of the non-renewable nature of the ligament, scar tissue repair is a demanding procedure, and the scar tissue within the ligament may need to be removed intraoperatively, making in situ anatomic repair very difficult for patients with shortened or heavily damaged and congenitally weak ligaments. The other type of approach is called graft reconstruction, where the function of the anterior talofibular ligament and the heel-fibular ligament is reconstructed through autologous ligaments or other grafts to strengthen the lateral stability of the ankle joint. The benefit of this type of surgery is that it strengthens the weak ligaments and is therefore indicated in individuals with severe ligamentous injuries or congenital weaknesses and in obese individuals who require this type of surgery to enhance their stability. Nilsonne was the first to report on this type of surgery, but it did not receive enough attention. Chrisman and Snook used a longitudinal split of the short peroneal tendon to better preserve the motor function of the muscle. The free end is passed through the fibula and then drilled through the heel bone and fixed to itself. In 1985, Snook modified their procedure by moving the graft back through the heel bone closer to the anatomic position of the heel-fibular ligament and avoiding the limitation of motion in the talofibular and subtalar joints. Good results were achieved in 38 of the 48 patients followed up. Leach et al. further modified this procedure by combining the anterior segment of the grafted tendon with the ATFL to better mimic the orientation of the ATFL, and reconstructed the ATFL, CFL, and TCLL (talofibular ligament) simultaneously, especially for combined talofibular instability, and this procedure is now the most widely used. Grondel repeated this procedure using a cadaveric ankle, and then incised the reconstructed ligament to see how parallel it was to the ATFL and CFL in order to assess the effect of the reconstruction. Watson-Jones tendon fixation taught a good reconstruction of the anterior talofibular ligament, but the heel-fibular ligament was more deviated when reconstructed by simulating the distal end of the short fibular tendon. Evan's tendon fixation Evan's procedure involves taking part or all of the distal end of the short peroneal tendon to preserve its distal end at the fifth metatarsal, with its free end passing anteriorly to posteriorly through the distal fibula or placed anterior to the fibula and sutured to the periosteum and then fixed to itself, and the belly of the short peroneal muscle is anastomosed to the long peroneal tendon. The intraoperative position of the foot and the tension of the suture affect the postoperative stability of the ankle joint and the restraint on the mobility of the subtalar joint. Anatomically the position of the transferred tendon does not reconstruct the ATFL or CFL but passes between them. Postoperatively, dorsioplantar flexion of the ankle will be slightly limited, anterior talar translation will be poorly controlled, and mobility of the subtalar joint will be reduced. Postoperative complications of osteonecrosis of the talus of vascular origin and rupture of the peroneus longus have also been reported. Huang He et al. performed a modified Evan's procedure on 42 patients with posterolateral instability at a follow-up of 2-6 years 4 patients still had abnormal activity X-rays showed ankle degeneration and unsatisfactory postoperative pain symptom relief. However, these functional reconstructive procedures were performed at the expense of weakening the peroneal muscle, which increased ankle instability and did not result in anatomical reconstruction. Dowling believes that the short peroneal tendon and the connective tissue between it and the CFL have a protective effect on the posterior stability of the ankle joint, so it is debatable whether the loss of the short peroneal muscle is worth reconstructing the lateral ligament. There are cadaveric trials reported in China using the third peroneal tendon or the long extensor tendon of the lesser toe to repair the anterior talofibular ligament alone, but there are no clinical reports yet. The significance of preserving the tendon nerve: the key nerve refers to the vascular nerve tissues that are wrapped around the outer membrane of the tendon to accompany the entry and exit of the tendon. The ligament is rich in nerve tissue and has a large number of receptors with different thresholds and fast and slow adaptations. Although there are many methods to repair and reconstruct ligament injuries, the results are often disappointing, producing functional imbalance, sensory loss, and muscle weakness syndrome. frank believes that this syndrome is due to afferent nerve blockage in the joint capsule and ligaments of the injured joint. therefore, it is important to reduce the destruction of joint sensation in surgical treatment. Preservation of the tendon button preserves both the blood supply and the nerves of the grafted tissue, which has a positive effect on adjunctive training and sensory reconstruction during the rehabilitation period and can lead to improved functional stability after joint injury. Another anatomical reconstruction of the lateral ligament using autologous peroneal membrane, fascia, dermis, and graft tendon has been continuously proposed. Guo Hongwang et al. performed peroneal membrane inversion repair in 30 patients with ankle instability, and postoperative pathological examination in three patients showed fibrous tissue ossification. Ken Nakata et al. performed anatomic repair of 24 lateral ligaments in 20 patients using dry irradiated allograft fascia. 60% of patients had satisfactory results, 35% had good results, and 5% had acceptable results at 3.1 to 10 years follow-up. There was no postoperative infection or limitation of activity. However, the improvement of postoperative pain symptoms was not evaluated. In the 1950s, Cumberland and Scals created criteria for ideal implantable materials: materials that are not physically denatured by tissue fluids, chemically inert, do not stimulate inflammation or foreign body reaction, are non-carcinogenic, do not cause allergic or hypersensitivity reactions, retain mechanical tension, can be placed in the desired shape, and can be sterilized. Therefore, there have been attempts to use hydrophilic materials. Therefore, some scholars have tried to reconstruct the lateral ligament using hydrophilic membrane and carbon fiber, but the first problem is the selection of the built-in material, which requires long-lasting tension and a certain elastic deformability. Due to the weak subcutaneous fat layer of the ankle joint and the high tension of the skin, the built-in material may increase the chance of incision infection and delayed healing, and these factors should be taken into account in the selection of the relatively exposed incision and the thickness of the built-in material in the outer ankle. Because of the lack of tendon reflex protection mechanism after the artificial material repair, whether the postoperative results are satisfactory remains to be observed in large samples and long-term follow-up.